Glycerophospholipids, also referred to as phospholipids, are ubiquitous in nature, are key components of the lipid bilayer of cells, and are involved in cell metabolism and signaling. The hydroxyl groups of the glycerol backbone of phospholipids are substituted by a hydrophilic phosphate head and hydrophobic tail composed of non-polar fatty acids. Glycerophospholipids may be subdivided into distinct classes, based on the nature of the polar headgroup such as for example: phosphatidylcholine (also known as PC or lecithin), phosphatidylethanolamine (PE) and phosphatidylserine (PS). In addition to serving as a primary component of cellular membranes and binding sites for intra- and intercellular proteins, some glycerophospholipids, such as phosphatidylinositols and phosphatidic acids are either precursors of, or are themselves, membrane-derived second messengers. Animal studies have shown that PS enhances neuronal membrane function and hence slows cognitive decline, especially in the elderly [McDaniel M A et al. Nutrition 19: 957-75 (2003) and Jorissen B L et al. Nutr Neurosci. 4(2):121-34 (2001)].
Many health benefits have been attributed to the consumption of certain fatty acids. For example, polyunsaturated fatty acids (PUFA) of the type omega-3 and omega-6, have several health benefits on cardiovascular disease, immune disorders and inflammation, renal disorders, allergies, diabetes, and cancer. Extensive clinical studies investigating the importance of omega-3 fatty acids such as Docosahexaenoic acid (DHA) in the brain, found that low levels of DHA are associated with depression, memory loss, dementia, and visual problems. Studies showed an improvement in the elderly brain function as blood levels of DHA increased. Furthermore, DHA may have importance in the field of brain function enhancement, baby formula fortification, diabetics and cancer.
The human body does not adequately synthesize DHA. Therefore it is necessary to obtain it from the diet. Humans obtain DHA from their diets, initially through the placenta, then from breast milk, and later through dietary sources, such as fish, red meat, animal organ meat and eggs.
Linoleic acid (LA, C18:2, ω-6) and α-linolenic acid (ALA, C18:3, ω-3), are classified as essential fatty acids (EFA). The body cannot synthesize them de novo, and they must therefore be obtained through food sources providing them “ready-made”. Both LA and ALA are needed for optimal growth and good health. Both LA and ALA are precursors of the ω-3 and ω-6 PUFA. LA is required for the synthesis of arachidonic acid (AA) (C20:4, ω-6), a key intermediate in the synthesis of eicosanoids, whereas ALA is used partly as a source of energy, and partly as a precursor for metabolites and longer chain PUFA. Within the human body LA and ALA can be elongated and desaturated to other more unsaturated fatty acids, principally AA and DHA (C22:6, ω-3), respectively.
Soybeans, egg yolk, bovine brain and fish are the major natural sources for obtaining and producing phospholipids, especially PS. The type of fatty acyl residues at the sn-1 and sn-2 positions in natural phospholipids vary, and their proportion in general depends on their source. For example, soybean is rich with LA fatty acid (about 54%) whereas fish derived lecithin is abundant with DHA fatty acid residue. The PS extracted from animal brain tissues, similar to human brain PS, has a fatty acid content which is characterized by relatively high levels of omega-3 moieties, compared to the levels of omega-3 found in plants, such as soy phospholipids. The bio-functionality of soybean PS in the improvement of cognitive function has been shown to be different from that of human brain PS [WO 2005/037848].